It may be detected from the former that the defect occurred in the memory cell in the wafer process. In this case, the memory cell of the spare formed as a redundant circuit is used instead of a defective memory cell.
A fuse is used for the switch from the state which uses the above-mentioned defective memory cell to the state which uses a spare memory cell. Generally as a fuse for this switch, the laser fuse cut by irradiating a laser beam from the outside is used.
When a laser fuse is used, before a resin seal is completed, it is necessary to irradiate laser at a fuse in the state where a semiconductor chip is uncovered. Therefore, it is required to use a laser trimming unit apart from a semiconductor manufacturing device. A laser fuse cannot be cut after a semiconductor chip is sealed with resin.
Then, after a semiconductor chip is sealed with resin, the fuse electrically cut by sending current has been developed as a means for the above-mentioned switch.
As a method for the above-mentioned switch, how to cut a wiring by sending current through a wiring, how to destroy a capacitor by applying the high voltage to a capacitor, how to destroy a gate insulating layer by applying the high voltage to a gate oxide film, and the way memory of a flash memory realizes the above-mentioned switch etc. can be considered. Hereafter, the method of cutting a wiring by sending current through a wiring is explained among these methods.
The fuse with which a wiring is cut by sending current through a wiring is called an electric fuse in this specification. As how to cut an electric fuse, in addition to a method using the electromigration phenomenon of an electric fuse known from the former, all, such as a method of making the melted fuse flow into the crack of the insulating layer surrounding an electric fuse which the inventors of the present application are developing as technology which is not opened to the public, and a method of using the elasticity in the width and height direction of an electric fuse, i.e., pinch effect, are included.
[Patent Reference 1] Japanese patent laid-open No. 2006-108413
[Patent Reference 2] Japanese patent laid-open No. 2001-24063
[Patent Reference 3] Japanese patent laid-open No. 2001-230325
[Patent Reference 4] Japanese patent laid-open No. 2006-13338